SVG seems to repaint way too many times during load (and is thus slow)
Maciej suggests that the xml code might not have the same sort of progressive load repaint throttling that html has.
If you load this SVG directly:
It takes about 2200ms uncached, about 70ms cached (using the PLT window).
Partly this is because the server is so slow, time curl -O http://www.carto.net/papers/svg/samples/canvas.svg reports 1.337s. However, the XML tokenizer also doesn't limit the rate of incremental repaints too, so we could be repainiting on each new data chunk to come in which could be suboptimal.
Fixed by bug 11984.
*** This bug has been marked as a duplicate of 11984 ***